Photosynthetic experiments with unicellular algae of different photosynthetic type

Felföldy, Lajos (1960) Photosynthetic experiments with unicellular algae of different photosynthetic type. A Magyar Tudományos Akadémia Tihanyi Biológiai Kutatóintézetének évkönyve, 27. pp. 193-200. ISSN 0365-3005

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Abstract

Photosynthetic curves of four algal strains (7K Chlorella vulgaris Beyer., 172 Kirchneriella contorta (Schmidle) Bohlin, 953 Coelastrum microvorum Näg., 3153 Chlorocloster terrestris Pascher.) investigated in a 3 mM KOH—K₂CO₃—KHCO₃ buffer system of different CO₂-deficiency by the usual Warburg method are discussed in this paper. On the basis of these experiments three photosynthetic types can be distinguished. In the first type only free carbon dioxide is utilized (Chlorella vulgaris), and photosynthesis decreases gradually parallel with the diminution of C02 content. There is no photosynthesis at high pH values and at a surplus of carbonate ions. The strain belonging to the second type can utilize both free carbon dioxide and hydrocarbonate ions, but its rate of photosynthesis becomes slower in a more alkaline carbonate-containing medium (Kirchneriella). The algae belonging to the third type can photosynthesize, after a certain lag-period, most vigorously in a solution containing hydro carbonates and a surplus of carbonates. Their photosynthesis in solutions containing free carbon dioxide, though starting just at the beginning of illumination, is slower than in buffers containing either hydrocarbonates or carbonates (Coelastrum and Chlorocloster). The experiments presented seem to support the hypothesis that the strains exhibiting a greater photosynthetic activity in solutions where carbonate ions predominate over hydrocarbonate ions are able to utilize the carbonate ions too. It is still undecided, whether the differences in photosynthetic rates in various buffer systems depend on the availability of carbon sources or on hydrogen ion concentration. The great pH tolerance in alkaline range of the strains investigated may perhaps be brought into connection with the chemical properties of their natural habitats. It seems to be an important assumption from the hydrobiological point of view that the ability of using hydrocarbonate (or carbonate) ions by planktonic algae is the result of a “training” taking place in a certain space of time. Thus, the main purpose of physiological research, when dealing with the ecology of photosynthesis in planktonic algae, should be to study the aptitude for this adaptation in the different species.

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